To me, the Fbass preamp is less colored than Bart preamps, and not as boomy as the Aggie. The only downside to the F pre IMO is that you can't cut the mids, it's boost only, but other than that, it's very good. I like all three preamps, but another one to throw into the mix would be the Ken Smith 18V system with the switches. I think that it's the best preamp that I've played, but the only downside is the cost which I think is quite pricey.

Also, the Fbass preamp was on the website last I checked with the diagrams and everything.